PHILADELPHIA (CBS) — Pop star Katy Perry had a surprise last night for her Philadelphia fans. As promised on stage during an appearance earlier this week at the Wells Fargo Center, she showed up at the steps of the art museum at midnight to climb the “Rocky” steps.

After two sold-out shows, Perry thanked her fans by showing up at the art museum to run the steps and take selfies.

“She did run up before most of the fans got there,” he tells KYW Newsradio. “When she was coming down, that’s when she got caught in about 100 or 150 fans. But she was great — she worked her way down and posed for lots of photos and selfies with lots of people.”

He adds, “I mean she didn’t have to do that she could have just wherever she stayed she could have just come and gone but instead she gave something back to the fans.”

One of those people was Courtney Scardecchio, from Bryn Mawr, Pa.

“I was the last person she took a photo with before she got in the car,” Courtney recounts. “I said, ‘Katy, can I get a selfie real quick?’ and she said, ‘Of course you can, sweetie,’ and she took my phone and took the pic. And then I said, ‘Thank you so much, you did so great tonight,’ and she said, ‘Thanks for coming out.’ ”

Michael Dougherty, of Norristown, celebrated his 17th birthday by running down the Rocky stairs with Perry:

“We were waiting in the center of the steps because we didn’t know which way she would come from, and then we noticed an Escalade (Cadillac SUV) pulled up top and she got out in her pepperoni jumpsuit and ran down the stairs.”

Kevin Rivera, who caught the crowd on his iPhone, raves, “She stood there and took pictures with everybody.”

At one point, Perry calmly instructs the crowd to take turns.

“Please move so another person can,” she heard saying on the video captured by Rivera.